The invention relates generally to apparatus for drying wet continuous strand which is advanced along its longitudinal axis. The invention is particularly directed to strand of the type which includes electrical wire coated with a plastic or rubber insulating material from an extruder. The wire is drawn from supply reels through the crosshead of an extruder where molten insulating material is applied to the wire in one or more layers. The coated wire then extends through a cooling trough containing cooling liquid such as water. The cooled, wet insulated wire emerges from the cooling trough and is conveyed through a drying trough to a series of stations, and finally to a winding station where the insulated wire is wound upon spools. Some of the intervening stations may include for example: an electron micrometer, a federal spark tester, a printer, and a measuring machine. Because of these stations it is essential that the insulated wire is completely dry when it leaves the drying trough. The most obvious problem is that caused by dripping water from incompletely dried wire which tends to accumulate into puddles on the floor and causes the reels and take-up machinery to rust. Wet wire also causes inaccurate readings as it passes through other stations such as the electron micrometer and federal spark tester. The most serious problem occurs in the printing station where electrical legends are applied to the wire. The presence of even a small amount of moisture on the wire will seriously impair printing on the surface of the wire.
Cooling troughs of the prior art comprise a V-shaped trough with a plurality of spaced openings at the bottom of the trough. Subatmospheric pressures created beneath the trough draws air around the moving wire through the openings. However, a serious drawback of this drying trough is that the subatmospheric pressure tends to draw the wire toward the openings at the surfaces of the trough and also blocks the openings, thereby restricting the flow of air through the openings. This abrasion of the insulating surface of the wire causes the surface to be scratched or otherwise damaged and the blocking of the openings in the trough by the wire prevents the wire from being completely dry as it emerges from the drying trough. These and other difficulties experienced by the prior art devices have been obviated by the present invention.
It is, therefore, an object of the invention to provide a strand drying apparatus in which the continuous strand material or wire is completely dried as it leaves the apparatus.
Another object of this invention is the provision of a strand drying apparatus in which abrasion of the strand material is substantially reduced.
A further object of the present invention is the provision of strand drying apparatus in which air is circulated around the entire outer periphery of the strand as it passes through the apparatus.
It is another object of the instant invention to provide a strand drying apparatus in which a trough is provided with a cover which conforms substantially to the shape of the strand for concentrating the airflow around the strand to a small area near the outer surface of the strand.
A still further object of the invention is the provision of a cover which locks into operating position on the trough and which is released from this position upon application of a predetermined amount of pressure in the direction of travel of the strand, as for example from a bump or slub extending from the surface of the strand.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.